Sensor design for capacitance sensing

ABSTRACT

Electrode configurations for reducing wobble error for a stylus translating on a surface over and between electrodes of a touch sensor panel are disclosed. In some examples, electrodes associated with a more linear signal profile are correlated with lower wobble error. In some examples, electrodes can have projections which can interleave with projections of adjacent electrodes. In some configurations, projections of adjacent electrodes can be interleaved in one-dimension; in other configurations, projections of adjacent electrodes can be interleaved in two-dimensions. In some configurations, the width and length of one or more projections in an electrode can be selected based on a desired signal profile for that electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/094,970, filed Apr. 8, 2016 and published on Nov. 3, 2016 as U.S.Patent Publication No. 2016-0320913, which claims the benefit under 35U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/154,057,filed Apr. 28, 2015, the contents of which are incorporated by referenceherein in their entirety for all purposes.

FIELD OF THE DISCLOSURE

This relates generally to touch sensor panels, and more particularly, toa touch sensor panel in which touch sensors have interleavingprojections in order to improve position calculation.

BACKGROUND OF THE DISCLOSURE

Touch sensitive devices have become popular as input devices tocomputing systems due to their ease and versatility of operation as wellas their declining price. A touch sensitive device can include a touchsensor panel, which can be a clear panel with a touch sensitive surface,and a display device, such as a liquid crystal display (LCD), that canbe positioned partially or fully behind the panel or integrated with thepanel so that the touch sensitive surface can cover at least a portionof the viewable area of the display device. The touch sensitive devicecan allow a user to perform various functions by touching the touchsensor panel using a finger, stylus, or other object at a location oftendictated by a user interface (UI) being displayed by the display device.In general, the touch sensitive device can recognize a touch event andthe position of the touch event on the touch sensor panel, and thecomputing system can then interpret the touch event in accordance withthe display appearing at the time of the touch event, and thereafter canperform one or more actions based on the touch event.

As touch sensing technology continues to improve, touch sensitivedevices are increasingly being used to compose and mark-up electronicdocuments. In particular, styli have become popular input devices asthey emulate the feel of traditional writing instruments. Theeffectiveness of a stylus, however, can depend on the ability toaccurately calculate the position of the stylus on a touch sensor panel.

SUMMARY OF THE DISCLOSURE

A stylus can be used as an input device for some capacitive touchpanels. In some examples, the touch sensor panel can have errors inposition detection, referred to herein as wobble error, when a stylus ispositioned between two of a plurality of touch sensors. In some cases,wobble error can correlate to the signal profile associated with touchsensors within the touch sensor panel. Specifically, narrower (i.e.,less linear) signal profiles are correlated with higher wobble error,and wider (i.e., more linear) signal profiles are correlated with lowerwobble error. Accordingly, in some examples, touch sensors can beconfigured such that the signal profile associated with each touchsensor is spread to be wider, and thus, more linear. In someconfigurations, touch sensors can include projections (e.g., branches)which can interleave with projections of adjacent sensors. In someexamples, projections of sensors can interleave in one dimension; insome examples, projections can interleave in two dimensions. In someexamples, the lengths and widths of each projection can be selectedbased on a desired signal profile for each touch sensor. In someexamples, each adjacent touch sensor can have substantially the samesignal profile, and the signal profile can be linear enough to reducewobble error.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary computing system capable of reducingwobble error according to examples of the disclosure.

FIG. 2 illustrates an exemplary self capacitance touch sensor panel thatcan be used to detect touch or hover (proximity) events according toexamples of the disclosure.

FIGS. 3A-3B illustrate examples of the disparity between actual positionand calculated position (wobble error) as a stylus moves along one axisof a touch sensor panel according to examples of the disclosure.

FIGS. 4A-4C illustrate example signal profiles as a stylus moves alongan axis of a touch sensor panel and corresponding levels of wobble erroraccording to examples of the disclosure.

FIGS. 5A-5B illustrate exemplary interleaving sensors interleaving inone dimension according to examples of the disclosure.

FIGS. 6A-6B illustrate exemplary interleaving sensors interleaving intwo dimensions according to examples of the disclosure.

FIG. 7 is a flowchart of an exemplary method for selecting sensordimensions in a two-dimensional interleaving configuration for use in atouch sensor panel according to examples of the disclosure.

FIGS. 8A-8B compare signal profiles corresponding to non-interleavingsensors and interleaving sensors according to examples of thedisclosure.

FIGS. 9A-9D illustrate example systems that can implement theinterleaving touch sensor configurations for reducing wobble erroraccording to examples of the disclosure.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples that can be practiced. It is tobe understood that other examples can be used and structural changes canbe made without departing from the scope of the disclosed examples.

A stylus can be used as an input device for some capacitive touchpanels. In some examples, the touch sensor panel can have errors inposition detection, referred to herein as wobble error, when a stylus ispositioned between two of a plurality of touch sensors. In some cases,wobble error can correlate to the signal profile associated with touchsensors within the touch sensor panel. Specifically, narrower (i.e.,less linear) signal profiles are correlated with higher wobble error,and wider (i.e., more linear) signal profiles are correlated with lowerwobble error. Accordingly, in some examples, touch sensors can beconfigured such that the signal profile associated with each touchsensor is spread to be wider, and thus, more linear. In someconfigurations, touch sensors can include projections (e.g., branches)which can interleave with projections of adjacent sensors. In someexamples, projections of sensors can interleave in one dimension, insome examples, projections can interleave in two dimensions. In someexamples, the lengths and widths of each projection can be selectedbased on a desired signal profile for each touch sensor. In someexamples, each adjacent touch sensor can have substantially the samesignal profile, and the signal profile can be linear enough to reducewobble error.

FIG. 1 is a block diagram of an example computing system 100 thatillustrates one implementation of an example touch sensor panel 120according to examples of the disclosure. Computing system 100 can beincluded in, for example, mobile telephone, digital media player,portable computing device, or any mobile or non-mobile computing devicethat includes a touch sensor panel, including a wearable device.Computing system 100 can include a touch sensing system including one ormore touch processors 102, peripherals 104, a touch controller 106, andtouch sensing circuitry. Peripherals 104 can include, but are notlimited to, random access memory (RAM) or other types of memory orstorage, watchdog timers and the like. Touch controller 106 can include,but is not limited to, one or more sense channels 108 and channel scanlogic 110. Channel scan logic 110 can access RAM 112, autonomously readdata from sense channels 108 and provide control for the sense channels.In addition, channel scan logic 110 can control sense channels 108 togenerate stimulation signals at various frequencies and phases that canbe selectively applied to the touch pixels of touch sensor panel 120. Insome examples, touch controller 106, touch processor 102 and peripherals104 can be integrated into a single application specific integratedcircuit (ASIC), and in some examples can be integrated with touch sensorpanel 120 itself.

Touch sensor panel 120 can be a self-capacitance touch sensor panel, andcan include touch a capacitive sensing medium having a plurality oftouch sensors. In some examples, touch sensor panel 120 can be part of atouch screen. In some examples, the plurality of touch sensors caninclude a matrix of small plates of conductive material that can bereferred to as touch pixels 122 or touch sensors. For example, touchsensor panel 120 can include a plurality of touch pixels 122, each touchpixel corresponding to a particular location on the touch sensor panelat which touch or proximity (i.e., a touch or proximity event) can besensed. A touch sensor panel using touch pixels 122 can be referred toas a pixelated self-capacitance touch sensor panel. During operation, atouch pixel can be stimulated and the self-capacitance of the touchpixel with respect to ground can be measured. As an object approachesthe touch pixel, the self-capacitance of the touch pixel can change.This change in the self-capacitance of the touch pixel can be detectedand measured by the touch sensing system to determine the positions ofone or more objects touching or proximate to the touch sensor panel. Insome examples, the object can be an active stylus, and theself-capacitance of the touch pixel can change in response to a couplingbetween the touch sensor and the active stylus. Touch pixels 122 can beformed as a matrix of substantially transparent conductive plates madeof materials such as Indium Tin Oxide (ITO) or Antimony Tin Oxide (ATO),although other transparent and non-transparent materials such as coppercan also be used. Some touch sensor panels can be formed by partiallyintegrating touch sensing circuitry and touch pixels into a displaypixel stack-up (i.e., the stacked material layers forming the displaypixels).

It is understood that while touch sensor panel 120 is described hereinas including touch pixels electrodes 122 (e.g., touch sensors), thetouch sensor panel can additionally or alternatively include rows andcolumns of conductive material. The operation of a touch sensor panelusing row and column electrodes can be similar to that of a touch sensorpanel using touch pixel electrodes. Additionally, it is understood thatin some examples, touch sensor panel 120 can also be configured as amutual capacitance touch sensor panel, though the description thatfollows will assume that the touch sensor panel is a self-capacitancetouch sensor panel having a plurality of touch pixel electrodes.

Computing system 100 can also include host processor 128 for receivingoutputs from touch processor 102 and performing actions based on theoutputs. For example, host processor 128 can be connected to programstorage 132 and a display controller, such as an LCD driver 134. The LCDdriver 134 can provide voltages on select (gate) lines to each pixeltransistor and can provide data signals along data lines to these sametransistors to control the pixel display image as described in moredetail below. Host processor 128 can use LCD driver 134 to generate animage on a display, such as a touch sensor panel. The image can be, forexample, an image of a user interface (UI), and can use touch processor102 and touch controller 106 to detect a touch on or near touch sensorpanel 120.

The touch input can be used by computer programs stored in programstorage 132 to perform actions that can include, but are not limited to,moving one or more objects such as a cursor or pointer, scrolling orpanning, adjusting control settings, opening a file or document, viewinga menu, making a selection, executing instructions, operating aperipheral device coupled to the host device, answering a telephonecall, placing a telephone call, terminating a telephone call, changingthe volume or audio settings, storing information related to telephonecommunications such as addresses, frequently dialed numbers, receivedcalls, missed calls, logging onto a computer or a computer network,permitting authorized individuals access to restricted areas of thecomputer or computer network, loading a user profile associated with auser's preferred arrangement of the computer desktop, permitting accessto web content, launching a particular program, encrypting or decoding amessage, and/or the like. Host processor 128 can execute software orfirmware implementing the algorithm for coded integration of aself-capacitance array according to examples of the disclosure. Hostprocessor 128 can also perform additional functions that may not berelated to touch processing.

Note that one or more of the functions described above, including theconfiguration of switches, can be performed by firmware stored in memory(e.g., one of the peripherals 104 in FIG. 1) and executed by touchprocessor 102, or stored in program storage 132 and executed by hostprocessor 128. The firmware can also be stored and/or transported withinany non-transitory computer-readable storage medium for use by or inconnection with an instruction execution system, apparatus, or device,such as a computer-based system, processor-containing system, or othersystem that can fetch the instructions from the instruction executionsystem, apparatus, or device and execute the instructions. In thecontext of this document, a “non-transitory computer-readable storagemedium” can be any medium (excluding a signal) that can contain or storethe program for use by or in connection with the instruction executionsystem, apparatus, or device. The non-transitory computer readablemedium storage can include, but is not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus or device, a portable computer diskette (magnetic), a randomaccess memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), anerasable programmable read-only memory (EPROM) (magnetic), a portableoptical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flashmemory such as compact flash cards, secured digital cards, USB memorydevices, memory sticks, and the like.

The firmware can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “transport medium” can be any mediumthat can communicate, propagate or transport the program for use by orin connection with the instruction execution system, apparatus, ordevice. The transport readable medium can include, but is not limitedto, an electronic, magnetic, optical, electromagnetic or infrared wiredor wireless propagation medium.

FIG. 2 symbolically illustrates an exemplary self capacitance touchsensor panel 200 that can be used to detect touch or hover (proximity)events with a stylus 208 according to examples of the disclosure. Insome self capacitance examples, touch sensor panel 200 can include aplurality of touch sensors 220 forming touch nodes. In some exampleseach touch sensor can be electrically isolated from the other touchsensors and configured to represent a particular X-Y location (e.g.,touch sensor 220) on the panel. Such touch sensor panels can be referredto as a pixelated self-capacitance touch sensor panels. A stylus 208 caninclude an electrode configured to capacitively couple to a touch sensorwith a capacitance Cs. In some examples, the stylus can be an activestylus, and the self-capacitance of the touch pixel can change inresponse to a coupling between the touch sensor and the active stylus.Each of the touch sensors can output its capacitance readings to one ormore touch sensing circuits (e.g., sense channels 108), which can beused to detect a touch or hover event. In other examples, the touchsensors can be configured as elongated sense rows and/or sense columns.

The distance between each adjacent touch node (e.g., the distance frommidpoint of one sensor to the midpoint of an adjacent sensor) in thesame row can be a fixed distance, which can be referred to as the rowpitch Pr for row sensors. The distance between each adjacent touch nodein the same column can have a fixed distance, which can be referred toas the column pitch Pc for column electrodes. In some examples, thepitch for row sensors and column sensors can be the same, but in otherexamples, Pr and Pc can be different.

Other touch sensor panel configurations, such as those with drive andsense lines and configured to operate as mutual-capacitance touch sensorpanels, are also contemplated for use with examples of the disclosure.In some mutual capacitance examples, an active stylus can generatestimulation signals (effectively operating as a drive electrode), andcolumn electrodes and row electrodes can effectively operate as touchsensors. During a stylus scan, one or more stimulation signals can beinjected by stylus 208 into the touch sensor panel 200 and can causemutual capacitive coupling between the stylus 208 and the row traces andcapacitive coupling between the stylus 208 and the column traces. Thecapacitance Cmr and Cmc can be transmitted to one or more touch sensingcircuits for processing. Additionally, in some examples, the touchsensor panel can include a stylus scan, a row scan, and a column scan,which can each operate as set forth above.

In some cases, an object, such as a stylus, may touch or hover at aposition not directly over a touch node (e.g., a midpoint of touchsensor 220), but in between two touch nodes. For example, a stylus maytouch or hover at a position between touch nodes (e.g., between touchsensors 220), or in the case of mutual capacitance, between two rowelectrodes, between two column electrodes, or both. In these examples,the signal sensed at a plurality of touch sensors 220 may be used toestimate the location of the touch or hover event. In some examples, acentroid estimation algorithm can calculate the location of the touch orhover event using the signal sensed at the plurality of touch sensors220. For example, the position of a stylus on a touch sensor panel alongan x-axis can be calculated by computing a weighted centroid defined inequation (1):

$\begin{matrix}{x_{calc} = \frac{\sum\limits_{i = {- N}}^{N}{x_{i}S_{i}}}{\sum\limits_{i = {- N}}^{N}S_{i}}} & (1)\end{matrix}$

where x_(calc) can be the calculated position along the x-axis, S_(i)can be the signal measured at the i^(th) sensor, such as a touch sensor,along the x-axis, and x_(i) can be the position of the i^(th) sensoralong the x-axis. It is to be understood that the centroid estimationalgorithm defined in equation (1) is given only as an example, and theconfigurations described herein need not be limited to such examples.Instead, the calculation of a touch or hover location of an object canbe accomplished using any appropriate method.

Ideally, as an object such as a stylus traverses between two touchnodes, the calculated position of the stylus on the touch sensor paneland the actual position of the stylus should be the same. In reality,the calculated position may be different from the actual position due tolimitations in the circuit configuration and the position estimationalgorithms used. Errors resulting from the disparity between calculatedposition and actual position as an object moves along a touch sensorpanel can be referred to as wobble error.

It can be useful to consider wobble error in the context of a stylusmoving along a single axis of a touch sensor panel with square sensors(e.g., sensors without interleaving projections). This concept isillustrated by example in FIGS. 3A-3B. FIGS. 3A-3B illustrate examplesof the disparity between actual position and calculated position as anobject, such as a stylus, moves along an x-axis of a customary touchsensor panel (e.g., a touch panel without interleaving sensors)according to examples of the disclosure. FIG. 3A illustrates a plot ofthe calculated position of the stylus versus the actual position of thestylus when calculating position using a weighted centroid algorithmincluding a subset of the sensors (e.g., five sensors) along an x-axis.In an ideal case, where calculated position and actual position are thesame, the plot can be a straight line at a 45 degree angle. However,because of non-idealities in the coupling between the stylus and thetouch sensor panel and the algorithm used to calculate stylus position,there can be non-ideal results that can appear as a wobble in the plotof FIG. 3A as the stylus moves between sensors along the x-axis. Inother words, the signal coupling between the stylus and touch sensorpanel and the calculated position metric can introduce an error incalculated position (discrepancy with actual position) that can cause awobble to be displayed when plotting the actual versus calculatedposition.

FIG. 3B illustrates a plot of the error in position calculation versusthe actual position when calculating position by taking a weightedcentroid including a subset of the sensors (e.g., five sensors) along anx-axis. The oscillation of the error plot can be representative of thewobble due to remaining error in the position calculation in aconventional touch sensor panel (e.g., a touch sensor panel havingsquare sensors without projections). Although FIGS. 3A-3B are describedwith reference to the x-axis, in some examples, similar effects can beobserved when moving the stylus across the touch sensor panel along they-axis.

It should be noted that the scope of this disclosure can extend beyondthe context of an active stylus coupling to touch sensors; however, theexamples of this disclosure focus on a stylus-touch sensor configurationfor ease of description. FIGS. 3A-3B relate to calculating positionusing a subset of the sensors; however, it should be understood that theposition could be calculated using any number of sensors, including allof the sensors in a touch sensor panel. It should also be understoodthat the plots in FIG. 4B are presented only as examples and should notbe understood to represent precise values or scale.

It can be useful to discuss the characteristics of the touch sensorconfiguration of a touch sensor panel in terms of the signal profilebetween a stylus and a touch sensor and the resulting wobble error. Thisconcept is explained by example with reference to FIGS. 4A-4C. FIGS.4A-4B relate to example signal profiles in an x-axis of two hypotheticaltouch sensors 411 and 412 having a pitch P1. FIG. 4B illustrates signalprofiles of sensors in two hypothetical configurations: a firstconfiguration (plots 443 and 444 shown in solid line) wherein the signalprofile is relatively non-linear, and a second configuration (plots 441and 442 shown in dotted line) wherein the signal profile is relativelylinear. The first and second configurations can differ, for example, insensor shape or orientation.

As shown in FIG. 4A, an object, such as a stylus 408, can be at adistance D1 above a touch sensor 411 and moved in an x-direction acrosstouch sensor 411 and 412. At each point along the x-axis, a signalcoupling Cs exists between the stylus and the touch sensor 411 andbetween the stylus and touch sensor 412, which varies as the stylusmoves across touch sensors 411 and 412. FIG. 4B illustrates a plot ofexample signal profiles, which can correlate to the signal Cs1 sensed ontouch sensor 411 and signal Cs2 sensed on touch sensor 412 from stylus408 as the stylus is moved in the x-direction. In some examples, such aswhen the stylus 408 is an active stylus, the signal Cs may represent asignal transduced by the stylus on the touch sensor. In some examples,the signal Cs may correspond to a self-capacitance of an object detectedby the touch sensor or a change in mutual capacitance between a drivetouch sensor and sense touch sensor. The x-axis of the plot in FIG. 4Bcan correlate to the position of the stylus in the x-axis relative tomidpoints M1 and M2 of touch sensors 411 and 412, and the y-axis of theplot in FIG. 4B can correlate to a normalized signal measurement at eachx-position along the x-axis.

Looking first at the relatively non-linear plots 443 and 444, as shownin FIGS. 4A-4B, the signal profile 443 for touch sensor 411 can have amaximum value when the stylus is at the midpoint M1 of touch sensor 411,and the signal level can decrease non-linearly as the stylus traversesthe x-axis away from the midpoint M1. When the stylus is over a midpointM2 of adjacent touch sensor 412, only a small amount of signal can bedetected at touch sensor 411, as shown at point 451. Looking now at themore linear example plots 441 and 442, touch sensor 411 can have amaximum signal Cs1 level 441 when stylus is at the midpoint M1 of touchsensor 411, and the signal level can decrease somewhat linearly as thestylus traverses the x-axis away from the midpoint M1. When the stylusis over a midpoint M2 of adjacent touch sensor 412, more signal Cs1 canbe detected by touch sensor 411, as shown at point 446.

FIG. 4C illustrates two example plots of the error in positioncalculation versus the actual position (i.e., wobble error) whencalculating position of a stylus by taking a weighted centroid includinga set of touch sensors along an x-axis. Each error plot 453 and 454corresponds to a set of touch sensors with touch sensor configurationscorresponding to plots 443-444 and 441-442, respectively. FIG. 4C issimilar to the plot of FIG. 3B, however, unlike the plot in FIG. 3B,which has an x-axis spanning the length of the touch sensor panel, thex-axis of FIG. 4C spans only the distance D2 (e.g., the distance of thepitch) immediately surrounding a single touch sensor as shown. In someexamples, the single oscillation in the error plots 453 and 454 shown inFIG. 4C can be similar to one of the many oscillations shown in FIG. 3B.For clarity, each of the example touch sensor configurations representedin FIGS. 4A-4C are assumed to have an equal pitch and midpoint.

If a signal profile is very non-linear, position estimation algorithms,such as that listed in equation (1), can produce higher wobble errorwhen a stylus is positioned between touch nodes. As shown in FIG. 4C,error plot 453 corresponding to the first touch sensor configuration(i.e., the less linear signal profile configuration) has more wobbleerror than error plot 454. Likewise, error plot 454 corresponding to thesecond touch sensor configuration (i.e., the more linear signal profileconfiguration) has relatively little wobble error as compared to errorplot 453 corresponding to the first touch sensor configuration. Thus, asillustrated in these examples, touch sensor configurations with morelinear signal profiles can correlate with lower wobble error.

The configurations and plots represented in FIGS. 4B and 4C arepresented only as examples of how a more linear signal profile can becorrelated with lower wobble error, and should not be understood torepresent specific values or scale. It should be understood that wobbleerror of a touch sensor panel can be determined by other factors inaddition to configuration of the touch sensors in the touch sensorpanel, such as, for example, position calculation algorithms used,stylus shape, and touch sensor pitch. Moreover, the solutions discussedin this disclosure can apply to configurations different from thosediscussed with respect to FIGS. 4A-4C, including configurations ofmutual capacitance, self-capacitance, and configurations wherein thetouch object is not a stylus.

As discussed above, touch sensors having a more linear signal profilecan correlate to a lower wobble error. Therefore, it can be beneficialto configure each touch sensor in a touch sensor panel to have a morelinear signal profile, by, for example, spreading the signal profileassociated with each sensor outwardly toward adjacent touch sensors.Thus, in some examples, it can be beneficial to utilize interleavingsensors, that is, sensors with interleaving projections. Theseinterleaving sensors will now be discussed below with reference to FIGS.5A-5B and 6A-6B.

FIGS. 5A-5B illustrate exemplary interleaving sensors having projectionsinterleaving in one dimension, referred to hereinafter asone-dimensional interleaving sensors. At left is a first sensor,referred to hereinafter as a left sensor 510; at right is a secondsensor, referred to hereinafter as a right sensor 530. It should benoted that, although these sensors are referred to as “left” and “right”sensors for convenience of explanation, left and right sensors 510 and530 need not be in any particular order.

In some cases, it can be useful to discuss the elements of interleavingsensors in the context of a hypothetical square sensor withoutprojections (e.g., the sensors in the configuration shown in FIG. 2),which can act as a baseline reference point in determining sensorparameters. In some cases, the hypothetical square sensor can have a rowpitch Pr_(SQUARE), column pitch Pc_(SQUARE), width W_(SQUARE), andheight H_(SQUARE). For example, in some cases the row and column pitchof the sensors (shown in FIG. 2 as Pr and Pc, respectively) can beselected using simple square sensors. Then, by using a square sensor asa reference, projections can be added while retaining the chosen columnpitch and row pitch, as will be discussed below. This approach can beconvenient if design constraints of a touch sensor panel require acertain pitch. In addition, in some cases, a desired surface area can bechosen for the square sensor. Then, using the square sensor as areference, sensors with interleaving projections can be designed to havethe same surface area. Although a hypothetical square sensor can be aconvenient reference point, it should be understood that the examplesensors disclosed herein are not dependent on a square sensor(hypothetical or otherwise) during operation or during the designprocess. Moreover, in other examples, other shapes, includingnon-rectangular shapes, may operate as baseline reference points.

For convenience of explanation, the hypothetical borders of a squaresensor (e.g., a hypothetical sensor without projections) are representedwith dashed lines in FIG. 5A, the square sensor borders having a widthW_(SQUARE) and height H_(SQUARE). The row pitch Pr_(SQUARE) is alsorepresented in FIG. 5B with dashed lines. As shown in FIG. 5A, both theleft and right sensors 510 and 530 can include one or more projectionsextending outwardly beyond the hypothetical square sensor borders in asingle direction (e.g., an x-direction). In addition, both left andright sensors 510 and 530 can include one or more recesses recedinginwardly from the square sensor borders in the single direction (e.g.,an x-direction). For convenience, the lengths of these projections andrecesses are given in terms of the length extending past the squaresensor borders (in the case of projections) or the length receding intothe square sensor borders (in the case of recesses). In some examples,each projection 511-512 in the left sensor 510 can correspond to arecess 535-536 in the right sensor 530. Likewise, each projection531-534 in the right sensor 530 can correspond to a recess 513-516 inthe left sensor 510. In other words, dimensions of projections in theleft sensor 510 can substantially match the dimensions of recesses inthe right sensor 530.

It can be helpful to conceptualize sensors with interleaving projections(e.g., interleaving sensors) as each having the shape of a squaresensor, but with certain areas “moved” from one sensor to another. Forexample, projections 511 and 512 of left sensor 510 can beconceptualized as being moved from within the square sensor borders ofright sensor 530 to outside of the square sensor borders of left sensor510, leaving recesses 535 and 536. In some cases, small areas of sensormaterial (e.g., areas 517 and 537) remain within the square sensorborders in order to connect the projections to the rest of the sensor,which can likewise correspond to missing areas (e.g., areas 518 and538). As indicated above, although dimensions are described herein withreference to a hypothetical square sensor, the sensors disclosed hereinneed not be described with reference to a square sensor, and need notconsider a square sensor in the design process.

The projections in the interleaving touch sensors have the effect ofspreading the sensor area outwardly toward adjacent sensors. As will bediscussed with reference to FIGS. 8A-8B, this can have the effect ofspreading the signal profile associated with the interleaving touchsensors. In some examples, touch sensors can be symmetric about one ortwo axes. In some examples, projections and areas of the touch sensorcan form a “T” shape. For example, projection 511 in left sensor 510 canbe visualized as forming a T when combined with sensor area 517. In someexamples, other projections and areas of the touch sensor can form an“L” shape. For example, projection 531 in right sensor 530 can bevisualized as forming an L when combined with sensor area 537. In somecases, two L-shaped areas can interdigitate with one T-shaped area, asillustrated in FIG. 6B.

The differences and similarities between left sensor 510 and rightsensor 530 will now be discussed. In some cases, the left and rightsensors can be different in form. In other words, the left and rightsensors can differ in either shape or orientation. For example, leftsensor 510 and right sensor 530 are different forms, as they differ inshape. In some cases, as in the sensors shown in FIG. 5A, the length L1of the projections in the left sensor 510 can match the lengths L1 ofthe projections in the right sensor 530, although in other examples,projection lengths may differ between sensors. In some configurations,the surface area of each projection within a sensor can be equal. Forexample, each of the projections 511-512 of left sensor 510 can all havea surface area defined by a length L1 and a width W1, and each of theprojections 531-534 of right sensor 530 can have a surface area definedby a length L1 and a width W2. Additionally, in some examples ofone-dimensional interleaving sensors, the individual surface area ofeach projection in the left sensor can be different from the surfacearea of each projection in the right sensor. For example, the surfacearea of each projection 511-512 in left sensor 510 (as defined above) isdifferent than the surface area of each projection 531-534 in rightsensor 530 (as defined above). However, despite the differences inindividual surface area of projections, the total surface area of leftsensor 510 can equal the total surface area of right sensor 530.

In some examples, the projections 511-512 of the left sensor 510 caninterleave with the projections 531-534 such that left sensor 510 andright sensor 530 are interdigitated, as shown in FIG. 5B. Returningagain to the concept of a hypothetical square sensor, in cases whereeach sensor is symmetric in the first dimension about the center, therow pitch between the left and right sensors 510 and 530, Pr₁ can matchthe square sensor pitch Pr_(SQUARE) (e.g., the pitch of a hypotheticalsquare sensor without projections). As shown, projections of the leftsensor 510 can be interdigitated with projections of the right sensor530. Although only two touch sensors are shown for clarity, the left andright sensors 510 and 530 can be patterned in an alternatingone-dimensional array across the length of a touch sensor panel. In somecases, left and right sensors can be patterned in a two-dimensionalarray with sensor projections interleaving in only one dimension. Adetailed explanation of the dimensions of one-dimensional interleavingsensors will be given later, but it should be noted here that thesensors illustrated in FIGS. 5A-5B are exemplary only. Other sensorswith one-dimensional interleaving within the scope of this disclosuremay include more or less projections, each of which may have differentdimensions and surface areas.

The details of the dimensions and operation of one-dimensionalinterleaving sensors will now be discussed. In general, it can beimportant that the attributes of one-dimensional interleaving sensorsare selected such that the signal profile associated with the leftsensor and the signal profile associated with the right sensor sharesubstantial symmetry, that is, the signal profile of each sensor issubstantially the same. Moreover, in some examples, it can be importantthat the attributes of the one-dimensional interleaving sensors areselected as to achieve a desired signal profile (e.g., a more linearsignal profile).

It can be important to the operation of the touch sensor panel that theleft and right sensors in a one-dimensional interleaving configurationhave substantially the same signal profile in the first dimension. Incases where the left and right sensors have different forms, attributesof the touch sensors may need to be selected such that, despite thedifferent form, the two sensors have substantially the same signalprofile. In this example, this can be achieved by setting eachprojection to be equal in length, L1, and likewise setting each recessto be substantially equal to L1 (e.g., recess areas 513-516 and 535-536have a length L1). In some examples, signal profiles corresponding toadjacent electrodes can be acceptably similar when the signal at anypoint along the x-axis of the first signal profile varies by less than27% from any corresponding point along the x-axis of the second signalprofile.

As discussed above, the linearity of a signal profile between a stylusand sensor can correlate with the amount of wobble error in the touchsensor panel, and the parameters of a sensor can determine the signalprofile associated with the sensor. Specifically, signal profiles thatare wider, and thus more linear, can correlate to lower wobble error. Insome interleaving sensors, the length of the projections (e.g., L1) candetermine the amount of spread in the signal profile (e.g., a largerprojection length L1 can result in a larger spread). Therefore, in somecases, the parameters of interleaving sensors (e.g., the length L1 ofprojections in sensors 510 and 530) can be selected such that the signalprofiles associated with each of the sensors are spread outward as to bemore linear.

In can be useful to consider the spread of a signal profile based onwhat percentage of the maximum signal amplitude is detected at themidpoint of an adjacent sensor (e.g., the amplitude at point 446 in FIG.4B). In some cases, a signal profile can correlate to less wobble errorwhen the signal profile at the adjacent sensor is 12-30% of the maximumsignal amplitude. In some cases, even less wobble error can correlate toa signal profile with 15-20% of the maximum amplitude detected at theadjacent sensor. In some examples, an ideal signal profile is producedfor sensors having a row pitch of 4 mm when the projection length ofeach sensor (e.g., length L1 in FIG. 5A) is equal to 0.7 mm, or 17.5% ofthe row pitch. It should be understood that these values are exemplaryonly, and acceptable signal profiles in other configurations maycorrespond to other values. Moreover, although the linearity of signalprofiles can reduce wobble error, increasing the linearity of signalprofiles can simultaneously reduce the maximum signal detected at eachtouch sensor, thus, potentially decreasing the signal-to-noise ratio(SNR) of the touch sensor panel. Therefore the desired signal profilemay also depend on the design goals and attributes of the touch sensorpanel.

FIGS. 6A-6B illustrate exemplary interleaving sensors having projectionsthat interleave in two dimensions according to examples of thedisclosure. FIGS. 6A-6B illustrate two-dimensional interleaving sensors,including a left sensor 610 and right sensor 630. It is understood thatthe terms “left” and “right” are for convenience only, and left andright sensors 610 and 630 need not be in any particular order. As shownin FIG. 6A, left sensor 610 and right sensor 630 can each have adifferent form (i.e., a different shape or orientation). Specifically,in this example, right sensor 630 is the same shape as left sensor 610,but is rotated 90 degrees with respect to the orientation of the leftsensor 610.

As with the one-dimensional interleaving sensors, it can be helpful todescribe the projections of the two-dimensional interleaving sensorswith reference to a hypothetical square sensor (e.g., a sensor withoutprojections). For convenience of explanation, borders of a hypotheticalsquare sensor are shown with dashed lines in FIG. 6A, along with aheight H_(SQUARE) and width W_(SQUARE). In addition, a row pitchPr_(SQUARE) and a column pitch Pc_(SQUARE) are shown with dashed linesin FIG. 6B. As shown in FIG. 6A, both the left and right sensors 610 and630 can include one or more projections extending outwardly beyond thesquare sensor borders in a two directions (e.g., some in the x-directionand some in the y-direction). In addition, both left and right sensors610 and 630 can include one or more recesses receding from the squaresensor borders in a two directions. For convenience, the length of eachprojection or recess is described with reference to the border of ahypothetical square sensor. For example, the length of a projection canrefer to the distance extended outwardly past the square sensor border;likewise, the length of a recess can refer to the distance recedinginwardly from the square sensor border. In some examples, eachprojection 611-616 in the left sensor 610 can correspond to a recess637-642 in the right sensor 630. Likewise, each projection 631-636 inthe right sensor 630 can correspond to a recess 617-622 in the leftsensor 610. In other words, dimensions of projections in the left sensor610 can substantially match the dimensions of recesses in the rightsensor 630. As described with reference to FIG. 5A above, projections ineach sensor can also be conceptualized as being area moved from withinthe square sensor borders of one sensor to outside of the square sensorborders of another sensor. For example, projections 614 and 615 of leftsensor 610 can be conceptualized as being moved from within the squaresensor borders of right sensor 630 to outside of the square sensorborders of left sensor 610, leaving recesses 639 and 640.

In some examples of two-dimensional interleaving sensors, the leftsensor can have the same shape as the right sensor, but in anorientation different from the right sensor. For example, in FIG. 6A,left sensor 610 can have the same shape as right sensor 630, but be inan orientation orthogonal to the orientation of the right sensor 630. Insome cases, the top and bottom sides of a sensor can each have anidentical set of first projections and first recesses (e.g., projectionsand recesses 617, 616, and 622, identical to 619, 613, and 620), andleft and right sides of a sensor can each have an identical set ofsecond projections and second recesses, different from the set of firstprojections and first recesses (e.g., projections and recesses 611, 618,and 612, identical to 615, 621, and 614). In some examples, each of thefirst projections and each of the second recesses can have a firstwidth, and each of the first recesses and each of the second projectionscan have a second width. For example, in left sensor 610, projections611, 612, 614, 615 and recesses 617, 619, 620, and 622 can have a widthW4, while projections 616 and 613 and recesses 618 and 621 can have adifferent width W3. In addition, elements with different widths can alsohave different surface areas. However, despite differences in theindividual surface areas of some projections, generally, the left andright sensors can each have the same total surface area. For example, inFIG. 6A, both left sensor 610 and right sensor 630 have the same shapeand dimensions, and thus, same surface area.

In some examples, the projections 611-616 of left sensor 610 caninterleave with the projections 631-636 of the right sensor 630 suchthat left sensor 610 and right sensor 630 are interdigitated in twodimensions. FIG. 6B illustrates left sensor 610 interdigitated withright sensor 630 in a first direction. In addition, the right sensor 630is interdigitated with a different left sensor 652 in a seconddirection, and the left sensor 610 is interdigitated with a differentright sensor 651 in the second direction. Returning again to the conceptof a hypothetical square sensor, in some cases, the two-dimensionalinterleaving sensors can have the same row pitch Pr₂ and column pitchPc₂ as a square sensor pitches Pr_(SQUARE) and Pc_(SQUARE), as shown.Although only four sensors are shown for clarity, the left and rightsensors 610, 630, 651, and 652 be patterned in an alternatingtwo-dimensional array across the area of the touch sensor panel. Adetailed explanation of the dimensions of two-dimensional interleavingsensors will be given later, but it should be noted here that thesensors illustrated in FIGS. 6A-6B are exemplary only. Othertwo-dimensional sensors with interleaving projections within the scopeof this disclosure may include more or less projections, which may havedifferent dimensions, surface areas, and shapes, includingnon-rectangular shapes. Moreover, in other examples, interleavingsensors may be arranged in a non-orthogonal array, such as an array in ahoneycomb pattern. In these cases, projections may interleave on moresides than four.

The details of the dimensions and operation of two-dimensionalinterleaving sensors will now be discussed. In general, it can beimportant that the attributes of two-dimensional interleaving sensorsare selected such that the signal profile in an x-direction issubstantially the same for each sensor, and the signal profile in ay-direction is also substantially the same for each sensor. Moreover, insome examples, it can be important that the attributes of thetwo-dimensional interleaving sensors are selected as to achieve adesired signal profile (e.g., a more linear signal profile in both thex-direction and y-direction). In examples where projection interleavingis in two dimensions, there can be two or more parameters to tune (e.g.,projection width, projection length, etc.) in order to achieve anacceptable signal profile, as will be explained in detail below.

It can be important to the operation of the touch sensor panel that theleft and right sensors in a two-dimensional interleaving configurationeach have substantially the same signal profile both in an x-directionand in a y-direction. In cases where the left sensor and right sensorare the same shape and orthogonally oriented, this condition can besatisfied when the left sensor and right sensor each have substantiallythe same signal profile in an x-direction (i.e., because the signalprofile in the x-direction of the left sensor is the signal profile inthe y-direction of the right sensor, and vice versa).

In some examples, the similarity of signal profiles between the leftsensor and right sensor in a two-dimensional interleaving configurationcan be a function of the ratio between the width of one or moreprojections and the pitch size of the sensors, or W:P. In this example,the column pitch of the sensors Pc₂ is equal to the row pitch Pr₂.Therefore, in this example, pitch P in the ratio W:P can representeither the column pitch or row pitch. In other examples, the width W cancorrespond to a width of a projection as measured in a first direction,and the pitch P can correspond to the pitch size in the first direction.Applying this function to the example sensors shown in FIG. 6A, thesimilarity of signal profiles between the left sensor and right sensorcan depend on the ratio of width W4 to the pitch size of the sensors. Inthe configuration shown in FIG. 6A, signal profiles associated with theleft and right sensors 610 and 630 can be acceptably similar when theratio of projection width W4 to pitch size P is between 0.35 and 0.375.

In some examples, to reduce wobble error in two-dimensions, theattributes of two-dimensional interleaving sensors can be selected as toachieve a desired signal profile (e.g., a more linear signal profile inboth the x-direction and y-direction). As explained above with referenceto FIGS. 3A-3B, signal profiles in an x-direction that are more linearcan correlate with lower wobble error in the x-direction, and signalprofiles in a y-direction that are more linear can correlate with lowerwobble error in the y-direction. In examples where the signal profile inthe x-direction substantially matches the signal profile in they-direction, and each projection has a same length (e.g., L2), thespread of a signal profile can be a function of the length of theprojections in relation to the pitch size of the sensor, or L2:P.

In the example shown in FIG. 6A, each projection has a length L2, asmeasured from the border of a hypothetical square sensor (e.g., a sensorwithout projections or recesses). Adjusting length L2 can, in someexamples, change the spread of the signal profile associated with theleft and right sensors 610 and 630. As with the one-dimensionalinterleaving sensors, it can be useful to consider the spread of asignal profile based on what percentage of the maximum signal amplitudeis detected at the midpoint of an adjacent sensor (e.g., the amplitudeat point 446 in FIG. 4B). As in the one-dimensional case, a signalprofile can correlate to less wobble error when the signal profile atthe adjacent sensor is 12-30% of the maximum signal amplitude. In somecases, even less wobble error can correlate to a signal profile with15-20% of the maximum amplitude detected at the adjacent sensor.

In some examples, an acceptable signal profile is produced for sensorshaving a row pitch of 4 mm when the projection length of each sensor(e.g., length L2 in FIG. 6A) is equal to 1 mm, or 25% of the pitch size.It should be understood that these values are exemplary only, andacceptable signal profiles in other configurations may correspond toother values. Moreover, although the linearity of signal profiles canreduce wobble error, increasing the linearity of signal profiles cansimultaneously reduce the maximum signal detected at each touch sensor,thus, potentially decreasing the signal-to-noise ratio (SNR) of thetouch sensor panel. Therefore the desired signal profile may also dependon the design goals and attributes of the touch sensor panel.

FIG. 7 is a flowchart 700 of an exemplary method for selecting sensordimensions in a two-dimensional interleaving configuration for use in atouch sensor panel according to examples of the disclosure. First, thepitch size P can be chosen (701) based on the configuration of the touchsensor panel or other design criteria. In some examples, this step canbe performed with reference to a hypothetical square sensor (e.g., asensor without projections). Second, projections can be either formed orsimulated (702). In some examples, the projections can be formed as toretain the chosen pitch size of the sensors (e.g., the pitch size of thesquare sensor) and to retain the chosen surface area of each sensor(e.g., the surface area of the square sensor). Third, the projectionwidth, W, can be selected (703) as to make the signal profiles of boththe left sensor and the right sensor to be equal in both the x-directionand y-direction. Fourth, the projections length, L, can be chosen (704)such that a desired signal profile is achieved. In some examples, anacceptable signal profile can have 12-30% of a signal detected when astylus is over the midpoint of an adjacent sensor, and even more wobbleerror reduction can be observed when this percentage is 15-20%.

FIGS. 8A-8B illustrate a comparison of signal profiles associated withsensors not having interleaving projections (shown in FIG. 8A) andsignal profiles associated with sensors having interleaving projections.FIG. 8A illustrates example signal profiles for two touch sensors 853and 854 in a non-interleaving configuration (e.g., a square sensorwithout projections such as the configuration shown in FIG. 2). FIG. 8Billustrates example signal profiles for two sensors 810 and 830 in aninterleaving configuration (e.g., one of the configurations shown inFIG. 5A-5B or 6A-6B). The x-axes of the graphs in both FIGS. 8A-8Brepresent the position of an object (e.g., a stylus) along anx-direction of a touch sensor panel, and the y-axes represent thenormalized signal amplitude detected at the respective sensor at eachpoint along the x-axis, as similarly described above with reference toFIGS. 4A-4B. For reference, the positions of example touch sensors arerepresented as rectangles under the x-axis in both FIGS. 8A-8B. In FIG.8B, touch sensors are shown as overlapping as to indicate theprojections which interleave in the x-direction (e.g., projections 614,615 and 633 in FIG. 6A). For ease of comparison, each of the exampletouch sensors corresponding to the signal profiles in FIGS. 8A-8B isassumed to have the same pitch, P1.

FIG. 8A illustrates an example of two signal profiles 851 and 852corresponding to two touch sensors without interleaving projections. Asshown in FIG. 8A, because each touch sensor does not have projections,the signal profile for each touch sensor can be narrower than signalprofiles corresponding to sensors with interleaving projections (e.g.,the signal profiles illustrated in FIG. 8B). For example, referring toFIG. 8A, if a stylus is positioned at the midpoint M1 of sensor 853, thesignal received on adjacent touch sensor 852 (point 857) can be onlyapproximately 9% of the maximum signal detected on touch sensor 854(e.g., the signal profile at midpoint M2).

FIG. 8B illustrates an example of two signal profiles 855 and 856corresponding to two adjacent example sensors 810 and 830 in anexemplary interleaving configuration (e.g., the configurationillustrated in FIG. 5A or 6A). Because projections interleave withprojections of an adjacent sensor, more signal is detected on a sensorthe stylus moves from the midpoint of the sensor. Thus, if a stylus ispositioned at the midpoint M1 of sensor 810, the signal received onadjacent touch sensor 830 (point 858) can be 15.3% of the maximum signaldetected on touch sensor 830 (e.g., the signal profile at midpoint M2).This spreading can make the signal profile of each touch sensor wider,and thus, more linear in the interleaving configuration. As discussedabove, signal profiles that are more spread, and consequently, morelinear, can correlate with lower wobble error in the touch sensor panel.

FIGS. 9A-9D illustrate example systems in which the interleaving sensorsfor reducing wobble error according to examples of the disclosure can beimplemented. FIG. 9A illustrates an example mobile telephone 936 thatincludes a touch sensor panel 924 that can implement the interleavingsensors for reducing wobble error according to various examples. FIG. 9Billustrates an example digital media player 940 that includes a touchsensor panel 926 that can implement the interleaving sensors forreducing wobble error according to various examples. FIG. 9C illustratesan example personal computer 944 that includes a touch sensor panel 928that can implement the interleaving sensors for reducing wobble erroraccording to various examples. FIG. 9D illustrates an example tabletcomputing device 948 that includes a touch sensor panel 930 that canimplement the interleaving sensors for reducing wobble error accordingto various examples. The touch sensor panel and computing system blocksthat can implement the interleaving sensors for reducing wobble errorcan be implemented in other devices including in wearable devices.

Thus, the examples of the disclosure provide various interleaving sensorconfigurations to make the signal profile associated with the touchsensor more linear, thus reducing wobble error and increasing touchsensor panel performance.

Therefore, according to the above, some examples of the disclosure aredirected to a touch sensor panel comprising: a plurality of electricallyisolated electrodes; a first electrode of the plurality of electrodeshaving a first form and a first surface area; a second electrode of theplurality of electrodes having a second form and a second surface area;wherein: the first electrode includes a first set of projections in afirst dimension, each projection of the first set of projections havingone of one or more first projection surface areas; the second electrodeincludes a second set of projections in the first dimension, eachprojection of the second set of projections having one of one or moresecond projection surface areas, each of the one or more secondprojection surface areas being different from each of the one or morefirst projection surface areas; the first electrode is interleaved withthe second electrode using the first set of projections and the secondset of projections; and the first surface area, including the respectivefirst projection surface areas, is substantially the same as the secondsurface area, including the respective second projection surface areasAdditionally or alternatively to one or more of the examples disclosedabove, in some examples, the plurality of electrically isolatedelectrodes are deposited on a first layer. Additionally or alternativelyto one or more of the examples disclosed above, in some examples, therespective first projection surface areas of each of the first set ofprojections are equal, and the respective second projection surfaceareas of each of the second set of projections are equal. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, a first projection of the first set of projections forms aT-shape; a first projection of the second set of projections forms anL-shape; and the first projection of the first set of projectionsinterdigitates with the first projection of the second set ofprojections. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the first form includes afirst shape that is symmetric about a first axis; and the second formincludes a second shape that is symmetric about the first axis.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first shape is symmetric about a secondaxis; and the second shape is symmetric about the second axis.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first form includes a first orientation anda first shape; the second form includes a second orientation and asecond shape; and the first form is different than the second form.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the first orientation of the first form is inthe first dimension; the second orientation of the first form isorthogonal to the first orientation; and the second shape of the secondform is the same as the first shape of the first form. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the first shape of the first form is different than the secondshape of the second form. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, the touch sensorpanel further comprises a third electrode having third form and a thirdsurface area; wherein the third electrode includes a third set ofprojections in a second dimension; the first electrode further includesa fourth set of projections in the second dimension; and the firstelectrode is interleaved with the third electrode using the fourth setof projections and the third set of projections. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the second dimension is orthogonal to the first dimension.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the third form of the third electrode is thesame as the second form. Additionally or alternatively to one or more ofthe examples disclosed above, in some examples, the first electrode isassociated with a first signal profile representing a plurality ofsignal measurements at the first electrode in the first dimension; andthe second electrode is associated with a second signal profilerepresenting a plurality of signal measurements at the second electrodein the first dimension. Additionally or alternatively to one or more ofthe examples disclosed above, in some examples, each of the first set ofprojections has a first width and first length; each of the second setof projection has a second width and second length; the first width andfirst length determine the first signal profile; the second width andsecond length determine the second signal profile; the first width andfirst length are optimized such that the first signal profile includes:a maximum signal measurement at a midpoint of the first electrode, and afirst signal measurement at a midpoint of the second electrode greaterthan or equal to 12% of the maximum signal measurement at the midpointof the first electrode; and the second width and second length areoptimized such that the second signal profile includes: a maximum signalmeasurement at the midpoint of the second electrode, and a second signalmeasurement at the midpoint of the first electrode greater than or equalto 12% of the maximum signal measurement at the midpoint of the secondelectrode. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the first signal measurement at themidpoint of the second electrode is less than 30% of the maximum signalmeasurement at the midpoint of the first electrode. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the first signal measurement at the midpoint of the secondelectrode varies by less than 27% from the second signal measurement atthe midpoint of the first electrode. Additionally or alternatively toone or more of the examples disclosed above, in some examples, the firstelectrode is further associated with a third signal profile representinga plurality of signal measurements at the first electrode in a seconddimension, different from the first, the third signal profile varies byless than 27% from the first signal profile. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the first electrode is further associated with a third signalprofile representing a plurality of signal measurements at the firstelectrode in a second dimension, different from the first, the thirdsignal profile varies by less than 27% from the first signal profile.

Some examples of the disclosure are directed to a method of forming atouch sensor panel comprising: forming a first and second electrode,wherein first projections of the first electrode interleave with secondprojections of the second electrode; selecting dimensions of the firstand second projections such that: the first projections each have afirst projection surface area; the second projections each have a secondprojection surface area, different from the first projection surfacearea; the first electrode has a first total surface area; and the secondelectrode has a total surface area equal to the first total surfacearea. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the method further comprisesselecting the dimensions of the first and second projections such that:the first projections are different from the second projections.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the method further comprises selecting thedimensions of the first and second projections such that: the firstprojections are symmetric about a first axis; and the second projectionsare symmetric about the first axis. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, the methodfurther comprises selecting the dimensions of the first and secondprojections such that: the first projections are symmetric about asecond axis; and the second projections are symmetric about the secondaxis. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the method further comprisesselecting the dimensions of the first and second projections such that:a baseline electrode without projections has a total surface area equalto the first total surface area; and a first signal measurement at thefirst electrode at a first distance from the first electrode is greaterthan a baseline signal measurement at the baseline electrode at thefirst distance from the baseline electrode. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the method further comprises selecting the dimensions of thefirst and second projections such that: a second signal measurement atthe second electrode at the first distance from the second electrode isgreater than the baseline signal measurement; and the second signalmeasurement substantially matches the first signal measurement.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, a distance between a midpoint of the firstelectrode and a midpoint of the second electrode is equal to the firstdistance; the first signal measurement is greater than or equal to 12%of a first maximum signal measurement at the first electrode at themidpoint of the first electrode. Additionally or alternatively to one ormore of the examples disclosed above, in some examples, the first signalmeasurement is less than 30% of the first maximum signal measurement.

Although the disclosure and examples have been fully described withreference to the accompanying drawings, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of the disclosure and examples as defined bythe appended claims.

1. A touch sensor panel comprising: a plurality of electrodes, includinga first electrode having a first form and a first surface area, and asecond electrode having a second form and a second surface area,wherein: a magnitude of the first surface area is substantially the sameas a magnitude of the second surface area, the first form of the firstelectrode is different than the second form of the second electrode, thefirst electrode includes a first projection having a first portion and asecond portion, the first portion of the first projection having a thirdform, and the second portion of the first projection having a fourthform, different than the third form, the second electrode includes afirst recess having a first portion and a second portion, the firstportion of the first recess having the third form, and the secondportion of the first recess having the fourth form, the first portion ofthe first projection is disposed within the first portion of the firstrecess, and the second portion of the first projection is disposedwithin the second portion of the first recess.
 2. The touch sensor panelof claim 1, wherein: a length of the first electrode and the secondelectrode along a first axis is a first length, and a distance between acenter of the first electrode and a center of the second electrode alonga second axis, different than the first axis, is the first length. 3.The touch sensor panel of claim 2, wherein the first electrode and thesecond electrode are disposed adjacent to each other along the secondaxis.
 4. The touch sensor panel of claim 1, wherein the first electrodeand the second electrode are disposed adjacent to each other along arespective axis, and the second electrode does not include a recess onan edge of the second electrode that is parallel to the respective axis.5. The touch sensor panel of claim 1, wherein the first projection ofthe first electrode has a T shape, and the first recess of the secondelectrode has the T shape.
 6. The touch sensor panel of claim 1, whereinthe plurality of electrodes are disposed in a same material layer of thetouch sensor panel.
 7. The touch sensor panel of claim 1, wherein thefirst electrode and the second electrode are disposed adjacent to eachother along a respective axis, and the first form and the second formare symmetric along the respective axis.
 8. The touch sensor panel ofclaim 1, wherein wherein the first electrode and the second electrodeare disposed adjacent to each other along a respective axis, the secondelectrode includes a plurality of projections that form the firstrecess, the first electrode is associated with a first signal profilerepresenting a plurality of signal measurements at the first electrodealong the first axis, and the second electrode is associated with asecond signal profile representing a plurality of signal measurements atthe second electrode along the first axis.
 9. The touch sensor panel ofclaim 8, wherein: the first projection of the first electrode determinesthe first signal profile; the plurality of projections of the secondelectrode determine the second signal profile; the first projection isoptimized such that the first signal profile includes: a maximum signalmeasurement at a midpoint of the first electrode, and a first signalmeasurement at a midpoint of the second electrode greater than or equalto 12% of the maximum signal measurement at the midpoint of the firstelectrode; and the plurality of projections are optimized such that thesecond signal profile includes: a maximum signal measurement at themidpoint of the second electrode, and a second signal measurement at themidpoint of the first electrode greater than or equal to 12% of themaximum signal measurement at the midpoint of the second electrode. 10.The touch sensor panel of claim 9, wherein: the first signal measurementat the midpoint of the second electrode is less than 30% of the maximumsignal measurement at the midpoint of the first electrode.
 11. The touchsensor panel of claim 9, wherein: the first signal measurement at themidpoint of the second electrode varies by less than 27% from the secondsignal measurement at the midpoint of the first electrode.
 12. The touchsensor panel of claim 1, wherein the plurality of electrodes isconfigured to sense signal from a stylus.
 13. A method of forming atouch sensor panel, the method comprising: forming a plurality ofelectrodes, including a first electrode having a first form and a firstsurface area, and a second electrode having a second form and a secondsurface area, wherein: a magnitude of the first surface area issubstantially the same as a magnitude of the second surface area, thefirst form of the first electrode is different than the second form ofthe second electrode, the first electrode includes a first projectionhaving a first portion and a second portion, the first portion of thefirst projection having a third form, and the second portion of thefirst projection having a fourth form, different than the third form,the second electrode includes a first recess having a first portion anda second portion, the first portion of the first recess having the thirdform, and the second portion of the first recess having the fourth form,the first portion of the first projection is disposed within the firstportion of the first recess, and the second portion of the firstprojection is disposed within the second portion of the first recess.14. The method of claim 13, wherein: a length of the first electrode andthe second electrode along a first axis is a first length, and adistance between a center of the first electrode and a center of thesecond electrode along a second axis, different than the first axis, isthe first length.
 15. The method of claim 13, wherein the firstelectrode and the second electrode are disposed adjacent to each otheralong a respective axis, and the second electrode does not include arecess on an edge of the second electrode that is parallel to therespective axis.
 16. The method of claim 13, wherein the plurality ofelectrodes are disposed in a same material layer of the touch sensorpanel.
 17. The method of claim 13, wherein the first electrode and thesecond electrode are disposed adjacent to each other along a respectiveaxis, and the first form and the second form are symmetric along therespective axis.
 18. A method of operating a touch sensor panel, themethod comprising: sensing touch signals at a plurality of electrodes,including a first electrode having a first form and a first surfacearea, and a second electrode having a second form and a second surfacearea, wherein: a magnitude of the first surface area is substantiallythe same as a magnitude of the second surface area, the first form ofthe first electrode is different than the second form of the secondelectrode, the first electrode includes a first projection having afirst portion and a second portion, the first portion of the firstprojection having a third form, and the second portion of the firstprojection having a fourth form, different than the third form, thesecond electrode includes a first recess having a first portion and asecond portion, the first portion of the first recess having the thirdform, and the second portion of the first recess having the fourth form,the first portion of the first projection is disposed within the firstportion of the first recess, and the second portion of the firstprojection is disposed within the second portion of the first recess.19. The method of claim 18, wherein: a length of the first electrode andthe second electrode along a first axis is a first length, and adistance between a center of the first electrode and a center of thesecond electrode along a second axis, different than the first axis, isthe first length.
 20. The method of claim 18, wherein the firstelectrode and the second electrode are disposed adjacent to each otheralong a respective axis, and the second electrode does not include arecess on an edge of the second electrode that is parallel to therespective axis.
 21. The method of claim 18, wherein the plurality ofelectrodes are disposed in a same material layer of the touch sensorpanel.
 22. The method of claim 18, wherein the first electrode and thesecond electrode are disposed adjacent to each other along a respectiveaxis, and the first form and the second form are symmetric along therespective axis.